MRI is a non invasive technique with broad diagnostic value. The technique has gained wide clinical acceptance and is of great importance in diagnostic medicine. However, despite significant technological advancements (increasing field strength and improvement in technology), applications of MRI are limited by an intrinsically low sensitivity.
Some alternatives to enhance its sensitivity have been developed which involve ex-vivo nuclear spin polarisation of agents, prior to administration and consequent in-vivo MR signal measurement.
EP1544634 discloses some of said alternative techniques, comprising among others, Dynamic Nuclear Polarisation (DNP), Para Hydrogen Induced (PHI) polarisation and Polarisation Transfer (PT) from a hyperpolarised noble gas.
WO9935508 describes a method for obtaining hyperpolarised high T1 agents by dynamic nuclear polarisation (DNP) whereby polarisation of a sample is carried out by a polarising agent or so-called DNP agent, which is a compound comprising unpaired electron.
WO2007064226 generally describes the use of paramagnetic metal ions, optionally added in chelated form, to enhance the hyperpolarisation level of a substrate, when subjected to hyperpolarisation MRI experiments.
We have now found that when a composition comprising acetic anhydride, a DNP agent and a suitable gadolinium complex of formula (A), is used in DNP experiments, an unexpectedly high degree of polarisation of the acetic anhydride system can be achieved. Even further, when the hyperpolarised acetic anhydride thus obtained is contacted with an aqueous carrier, the anhydride is converted to acetic acid, maintaining the high degree of polarisation and thus employable e.g. as MRI contrast agent.
Hence, according to the invention, the gadolinium complex of formula (A) is particularly advantageous when used as DNP hyperpolarisation enhancer for acetic anhydride based systems. For these and other advantages, which may be better appreciated by the skilled person upon reading the detailed description of the invention, the present invention provides a substantial innovative contribution over the state of the art.